vi: make autoindent respect expandtab setting

Autoindent took a copy of the indent from a neighbouring line, which
may not have respected the expandtab setting.

Determine the target column and construct a suitable indent.  This
will consist entirely of spaces if expandtab is enabled or an
efficient combination of tabs and spaces otherwise.

function                                             old     new   delta
char_insert                                          719     741     +22
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 1/0 up/down: 22/0)               Total: 22 bytes

Signed-off-by: Ron Yorston <rmy@pobox.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 19 insertions, 13 deletions

diff --git a/editors/vi.c b/editors/vi.c
index c4f3b9660..36116e677 100644
--- a/editors/vi.c
+++ b/editors/vi.c
@@ -2111,6 +2111,7 @@ static char *char_insert(char *p, char c, int undo) // insert the char c at 'p'
 #if ENABLE_FEATURE_VI_SETOPTS
         char *q;
         size_t len;
+        int col, ntab, nspc;
 #endif
 
         if (c == 22) {          // Is this an ctrl-V?
@@ -2151,7 +2152,7 @@ static char *char_insert(char *p, char c, int undo) // insert the char c at 'p'
                 }
 #if ENABLE_FEATURE_VI_SETOPTS
         } else if (c == '\t' && expandtab) {    // expand tab
-                int col = get_column(p);
+                col = get_column(p);
                 col = next_tabstop(col) - col + 1;
                 while (col--) {
 # if ENABLE_FEATURE_VI_UNDO
@@ -2186,23 +2187,28 @@ static char *char_insert(char *p, char c, int undo) // insert the char c at 'p'
                         showmatching(p - 1);
                 }
                 if (autoindent && c == '\n') {  // auto indent the new line
-                        // use current/previous line as template
+                        // use indent of current/previous line
                         q = openabove ? p : prev_line(p);
                         len = strspn(q, " \t"); // space or tab
-                        if (openabove) {
-                                p--;            // this replaces dot_prev() in do_cmd()
-                                q += len;       // template will be shifted by text_hole_make()
-                        }
+                        if (openabove)
+                                p--;    // indent goes before newly inserted NL
                         if (len) {
-                                uintptr_t bias;
-                                bias = text_hole_make(p, len);
-                                p += bias;
-                                q += bias;
+                                col = get_column(q + len);
+                                if (expandtab) {
+                                        ntab = 0;
+                                        nspc = col;
+                                } else {
+                                        ntab = col / tabstop;
+                                        nspc = col % tabstop;
+                                }
+                                p += text_hole_make(p, ntab + nspc);
 # if ENABLE_FEATURE_VI_UNDO
-                                undo_push_insert(p, len, undo);
+                                undo_push_insert(p, ntab + nspc, undo);
 # endif
-                                memcpy(p, q, len);
-                                p += len;
+                                memset(p, '\t', ntab);
+                                p += ntab;
+                                memset(p, ' ', nspc);
+                                p += nspc;
                         }
                 }
 #endif